DESCRIPTION: The proposed research will explore the development of infants' responses to actions carried out by others. The experiments all make use of the visual-habituation method. In preliminary research, the investigator has found that, at 9 and (to perhaps a lesser extent) 5 months of age, infants selectively encode the goal of grasping actions performed by a hand; other actions, such as pointing to an object, or touching an object with the back of the hand, are not selectively encoded, nor are actions performed by inanimate objects (e.g., a rod or crane). Further results showed that 12-month-old infants do selectively encode pointing actions. These results suggest that young infants have a system of knowledge to guide their reasoning about human actions, which undergoes development during the first year. The proposed experiments explore the nature and development of this knowledge. They explore: 1) infants' responses to a wide range of actions and corresponding inanimate functional relations; 2) infants' ability to categorize actions as goal-directed or not; 3) infants' ability to integrate information from simultaneous actions; and, finally, 4) infants' responses to means-end sequences involving two distinct actions on two distinct objects. Taken together, these experiments should contribute to our understanding of what are the roots in infancy of early psychological knowledge.